Effect of PEG–salt mixture on the gelation temperature and morphology of MC gel for sustained delivery of drug

Gelation temperature of MC was reduced from 59 °C to 54 °C with the addition of 10% PEG. Sodium tartrate (NaT) and sodium citrate (NaC) were added to the MC–PEG solution to further reduce the gelation temperature close to physiological temperature. Different techniques were used to measure the gelation temperature of all formulations. It was observed that NaC was more effective in reducing the gelation temperature of MC–PEG combination than NaT. Environmental scanning electron microscopy (ESEM) images of hydrogels containing NaC and NaT showed that NaC containing hydrogel having an interconnected microporous structure instead of the hollow rod like structure as in the case of NaT containing hydrogel. In vitro drug release studies showed that drug release time increased from 6 to 9 h by only changing the type of salt from NaT to NaC in MC–PEG combination.